1. Field of the Invention
The present invention relates to an object detection system and more particularly to an object detection system for detecting an object from a captured image captured by an image capture unit.
2. Description of the Related Art
In recent years, the development of technologies has been in progress in which by a passenger vehicle or a robot provided with artificial intelligence is equipped with a plurality of image capture units such as a pair of CCD (Charge Coupled Device) cameras to capture images of surroundings thereof and captured images are analyzed to measure positions and distances to objects which surround the vehicle or robot so as to detect the objects (for example, refer to JP-A-5-114099, JP-A-5-265547, JP-A-10-283461, and JP-A-10-283477).
In the technologies described above, in order to prevent the lenses of the CCD cameras from getting dirty and eliminate a failure of the cameras due to rain drops or the like sticking to the image capture units, the image capture units are normally designed to be mounted on an interior side of the windscreen of the vehicle or a glass is designed to be disposed in front of the image capture units so as to prevent the direct contact of the image capture units with outside air.
However, when dirt or rain drops stick to the windscreen or the glass disposed in front of the image capture units, images on which objects are captured are distorted or extra light is superposed due to the dirt or rain drops so sticking to the windscreen or the glass to thereby weaken signals from the objects themselves. Whereby the distances to the objects or the positions of the objects are caused to vary largely, causing a problem that the reliability in detection is decreased.
To cope with this problem, in JP-A-2001-273494, for example, there is proposed an object recognition system having a failsafe function to cause the system for observing by itself whether or not an object is being detected properly. In addition, in JP-A-6-230115 and JP-A-9-171075, there are proposed distance measuring systems provided with a radar system and an image capture unit to enhance the reliability in detection of objects.
However, the object recognition system described in JP-A-2001-273494 is such that a captured image is divided into a plurality of windows, a measured distance is calculated for each window by a stereo matching operation, and clustering is applied to the windows. Whereby objects are recognized based on clusters determined as valid, and although the reliability in object recognition is increased. When it rains comparatively heavily, the number of clusters determined as invalid is increased, and therefore, there is a possibility that the object recognition itself cannot be implemented.
In addition, in the object recognition systems described in JP-A-6-230115 and JP-A-9-171075, since the radar system is provided in addition to the image capture unit, highly reliable object detection is made possible under wide weather conditions from fine to rainy weathers. However, since the plurality of distance measuring systems including the radar system are necessary, there is a problem that it is difficult to realize a reduction in market price of the systems.